A refrigerant circuit in which more than one type of refrigerant, the boiling points of which are different from each other (non-azeotropic mix-type refrigerant) is circulated has been used as the refrigerant circuit of a residential heat pump apparatus. The conventional type of refrigerant circuit using the non-azeotropic mixed-type refrigerant is not required to separate the mixed-type refrigerant in a short period. Because the switching condition from the cooling operation to the heating operation or from the heating operation to the cooling operation of the residential heat pump apparatus usually occurs only a few times during a year.